Masking out an object with another object.

# 1 23-11-2012 , 04:45 PM

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Hey guys,

I was wondering if there was a way to "mask" out (parts of) a mesh with another mesh.

For instance we have a green mesh and a red mesh here: https://i.imgur.com/w3T2n.jpg?1

The green mesh is the mask, and the red mesh is the object I like a part to be masked out. I'd like to mask out the part both meshes intersect (like a boolean) and make the masked out parts have no holes. also I'd like to have the option to animate the green "mask" mesh.

Is there any way to create this?

Thanks in advance.

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# 2 23-11-2012 , 05:26 PM

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ctbram did this tutorial see link................dave

tip animate boolean diffence - YouTube

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# 3 23-11-2012 , 05:51 PM

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Wow, didn't expected that it was this easy. thanks a lot!

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# 4 23-11-2012 , 06:05 PM

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I do see that this way is as buggy and somewhat restricted as booleans in general. It won't work in maya 2012 (only seems to work in maya 2010 here and didn't tried out complex models yet)

Is there perhaps a more controlled way/way with more options(like still having the ability to change/deform the mask/boolean shape)?

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# 5 23-11-2012 , 06:28 PM

The thin red line
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Could you show the model you are going to use and what you want to do with it...........dave

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# 6 24-11-2012 , 08:46 AM

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It is not that booleans are buggy, but rather they have some very specifics rules inorder for them to work properly. In almost every case where they fail it is the result of not following the rules.

I have maya 2011, 12, and 13 and have tested the example in the video on all of them and it works as demonstrated. In fact if you look closely at the demo you can see that I was using maya 2012.

Therefore, it is more likely that there is an issue with your geometry that is preventing it from working as you expect.

Can you show us the geo you are trying to boolean and possibly link the .ma file?

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 24-11-2012 at 08:49 AM.

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# 7 24-11-2012 , 09:00 AM

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Boolean operations don’t work as expected
Boolean operations may sometimes produce unexpected results if the original objects are not closed volumes, or if they contain nearly coincident vertices. Other conditions to note include:
The region of intersection should not contain border edges. You can display border edges by selecting Display > Polygons > Border Edges.
Avoid meshes that are non-manifold in nature. That is, an edge does not connect to more than two faces.
The normals on the meshes must consistently point outwards on the volumes. You can view the normals on a mesh using Display > Polygons > Face Normals. You reverse face normals using Normals > Reverse.
Before applying a boolean operation, fill any openings in the original objects (for example, use Mesh > Fill Hole), and then use the Merge feature (Edit Mesh > Merge) with a suitably small Threshold tolerance to merge vertices that are effectively coincident.
Ensure the meshes involved do not have very small faces and edges. Booleans operations do not work on meshes that have zero area (or very small) faces or zero length (or very short) edges.
The boolean feature automatically checks for and removes very small faces and edges via the Use Thresholds option on the polyBoolOp node. This controls two threshold settings that determine whether small faces and edges are checked for and removed automatically during the boolean operation. The default setting is on.
- The Vertex Distance Threshold checks for zero length edges (or very short edges). Any vertices closer than the value specified will automatically be merged into one vertex.
- The Face Area Threshold checks for zero area faces (or very small faces). Any faces with an area smaller than the value specified will automatically be collapsed into one vertex.
Note
The default threshold settings are a good starting point. If the boolean operation fails, you can experiment with the threshold settings to achieve best results. Increasing either the Vertex Distance Threshold or the Face Area Threshold on the polyBoolean node by too large a value will cause portions of the mesh to disappear.
Maya runs out of memory when using the boolean operations
Using booleans on large polygonal objects is a memory intensive operation. Maya can run out of memory if this operation is performed many times on large polygonal objects.
To reduce the possibility of running out of memory, keep the undo queue length small or flush the undo queue every now and then when performing boolean operations on large polygonal objects.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 8 24-11-2012 , 09:41 AM

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Just to add to what Rick has said, the boolean operating can work but some times will delete small faces on the mesh its always a good idear to have a quick check after you have done one..............dave

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# 9 25-11-2012 , 03:15 AM

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It was in the list just buried in all the other rules....

Ensure the meshes involved do not have very small faces and edges. Booleans operations do not work on meshes that have zero area (or very small) faces or zero length (or very short) edges.

One of the reasons booleans get a bad rap is that there are a lot of rules and so it's easy to break one or more of them and then spend a lot of time scratching your head trying to discover the problem.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 25-11-2012 at 08:39 PM.

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# 10 27-04-2013 , 10:25 AM

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does anyone know how they did this?

could anyone tell how midway was able to animate their characters with the fatalities that they have?
like masking out meshes so that the character appears to be teleporting. or cutting through meshes so as the character appears to be severing the opponent's head.. etc...

Mortal Kombat (2011) - Freddy's Dead: The MK Nightmare (Xbox 360) - YouTube user added image

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Masking out an object with another object.

does anyone know how they did this?

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